East side of Teton Range, WY (pan)

Teton Range, a range in the Rocky Mountains or North America.

alpine, glaciated, glacial, rugged, granite, granitic,

Marine Transgression diagram

Marine transgression

If you look at Time 1, you can see a coastline in cross-section, with sand being deposited closest to shore, mud a little farther out, and eventually carbonate material even farther out. As sea levels rise in Time 2, the sites of deposition for these materials migrates landward, putting mud deposition on top the earlier sand deposition and so on. In time 3, the sequence moves even farther landward, resulting in carbonate over mud over sand. If these materials become preserved and turned into rock, they form the sequence sandstone overlain by shale overlain by limestone – just what we see on top the Great Unconformity. (Image ID# transgression)

Great Unconformity in Wyoming

Great unconformity on the west side of the Teton Range in Wyoming.

The yellow arrow points to the contact between the Cambrian Sandstone and underlying Precambrian metamorphic rock. This area is called the Great Unconformity of Powell, named after it’s first observer John Wesley Powell in 1869. (Image ID# sru-14e)